The present invention relates to the purification of minerals. More particularly, the invention may be applied to the purification of suitable heavy minerals, in particular, baddeleyite.
In the course of seeking suitable ore dressing methods for the purification of zirconium ores, in particular baddeleyite, difficulties were experienced in achieving a satisfactory liberation of different mineral species from one another for purposes of physical separation. Normally, grinding of the ore is resorted to for that purpose. However, grinding to an extent sufficient to liberate comparatively small strongly cohering particles of different mineral species from one another resulted in an unfavorable particle size distribution for subsequent ore dressing steps, in particular too high a content of fine particles.
One particular aspect of the invention is concerned with the purification of substantially chemically e.g., acid resistant minerals forming particles traversed by chemically, e.g., acid susceptible zones with which at least some of the impurities are associated, which impurities may themselves be chemically, e.g., acid resistant. Typical examples are to be found amongst certain non-magnetic, e.g., zirconium minerals, associated with magnetic minerals, e.g. ilmenite or ilmenite/magnetite, both components being acid resistant. It has been found surprisingly herein, that such associations are often held together by a cement, usually a carbonatic or silicious material, substantially more readily attached chemically, e.g. by acids than the resistant minerals just referred to, thus making it feasible to advantageously liberate the chemically resistant components from one another where previously mechanical grinding had to be resorted to with resultant undesirable particle size distribution.
A further aspect of the invention is based on the surprising discovery that substantially the same process conditions can be applied with particular success to free acid resistant heavy minerals, e.g. zirconium minerals, in particular baddeleyite from natural radioactive contamination, in particular thorium and uranium contamination.
The invention has proved itself particularly valuable in the context of upgrading baddeleyite occurring in low concentration in rocks of the Phalaborwa igneous complex (in particular the Foskorite and carbonatitite ores of the Loole Kop plug), in particular in association with apatite, biotite, bornite, brucite, calcite, chalcocite, pyrite, chondrodite, dolomite, ilmenite, magnetite, olevine, phlogopite, pyroxene, serpentine, spinel, valeriite and vermiculite in rocks usually associated with carbonatite intrusives, in particular, the rock which has become known as Foskorite. It is possible to obtain from such rocks concentrates of valuable minerals such as apatite and various copper minerals in such a manner that tailings are obtained which are suitable for the recovery of baddeleyite therefrom.
Whereas the process in accordance with the present invention has been found particularly suitable in connection with this particular problem of upgrading, the process is also considered suitable whenever baddeleyite of substantially similar mineralogical characteristics and with similar forms of contamination is found.